Answer:
The number of U.S stamp he has is 120.
Step-by-step explanation:
John has us and foreign stamps in his album. the ratio of the number of U.S stamps to foreign stamps is 5:2.
After Paul gives him 12 foreign stamps the ratio becomes 2:1.
Now, to find the number of U.S stamps.
Let the U.S stamps be [tex]x.[/tex]
And the foreign stamps be [tex]y.[/tex]
Now, to solve by using cross multiplication method:
So, the ratio is:
[tex]\frac{x}{y} =\frac{5}{2}[/tex]
By cross multiplying we get:
[tex]2x=5y[/tex]
Dividing both sides by 2 we get:
[tex]x=\frac{5y}{2}[/tex]......(1)
Now, after Paul gives him 12 foreign stamps the ratio becomes:
[tex]\frac{x}{12+y} =\frac{2}{1}[/tex]
By cross multiplying we get:
[tex]x=24+2y[/tex]
Putting the value of [tex]x[/tex] as we get in above equation (1):
[tex]\frac{5y}{2} =24+2y[/tex]
Multiplying both sides by 2 we get:
[tex]5y=48+4y[/tex]
Subtracting both sides by 4y we get:
[tex]y=48.[/tex]
The number of foreign stamps = 48.
Now, to get the number of U.S stamps by putting the value of [tex]y[/tex] in equation (1):
[tex]x=\frac{5\times 48}{2}[/tex]
[tex]x=\frac{240}{2}[/tex]
[tex]x=120.[/tex]
Therefore, the number of U.S stamp he has is 120.
